Pool chlorine may give children asthma

INDOOR swimming pools could be contributing to the soaring number of Welsh children affected by asthma.

INDOOR swimming pools could be contributing to the soaring number of Welsh children affected by asthma.

Research published today has found that the gases used to keep swimming pools clean could be causing an increase in asthma. The Belgian research said the prevalence of childhood asthma and wheezing rises by around 2% to 3% for every indoor swimming pool per 100,000 of the population across Europe.

Wales has the fourth highest rate of childhood asthma in the world - almost one in three 13 and 14-year-olds have the disabling condition.

The rise in asthma has previously been linked to the so-called hygiene hypothesis, which suggests children are no longer exposed to a wide range of allergens and microbiological irritants at an early age, as Western societies have become more hygienic.

Deprivation and exposure to tobacco smoke, as well as a genetic link, have helped to exacerbate Wales' asthma problems.

But more recent research has found that young children who regularly go swimming have a higher risk of asthma.

The authors of the study, from the Catholic University of Louvain, in Brussels, said, "According to this new hypothesis, the asthma rise in children in industrialised countries would thus result less from the declining exposure to microbiological agents - the hygiene hypothesis - than to the increasing exposure to the harmful by-products of chlorination, the most commonly used method to achieve hygiene in developed countries. Of these by-products, probably the most toxic to the respiratory tract is nitrogen trichloride or trichloramine, the gas which gives indoor swimming pools their typical smell and which is released in pool air when chlorine-based disinfectants destroy organic matter brought by swimmers."

The researchers analysed the rates of wheezing, asthma, hay fever, allergic rhinitis, and atopic eczema, reported in the International Study of Asthma and Allergies in Childhood (ISAAC), by video or written questionnaire.

The study involved almost 190,000 teenagers - aged 13 and 14 - from 21 countries. The Belgian pair calculated the number of indoor chlorinated swimming pools per 100,000 of the population in each country. After taking account of potential influential factors, such as the gross domestic product (GDP) of a country, climate, and altitude, the prevalence of asthma and wheeze was strongly associated with the number of indoor pools per 100,000 of population. The UK has the highest number of indoor chlorinated swimming pools in Europe more than six per 100,000 population.

Welsh Assembly Government figures show there are 139 public swimming baths in Wales.

The research findings showed a clear East-West divide in indoor pool availability and rates of asthma. The rate of wheezing rose by 3.39% for every additional indoor chlorinated swimming pool. The rate of asthma rose by 2.73%.

The authors said the rise of asthma in Western Europe could at least partly be attributed to the increasing exposure of children to the by-products of chlorine in the air and water of indoor swimming pools. They suggest the long term effects of chlorine by-products on children's respiratory health should be thoroughly evaluated, pools should be properly ventilated, and levels of chlorine by-products regulated.

A spokesperson for Asthma UK said, "Swimming is an excellent form of exercise for children with asthma as the warm humid air in the swimming pool is less likely to trigger asthma symptoms.

"We do recognise however that the chemicals present in heavily chlorinated pools may be important in making the airways more irritable and further research is needed to understand this association."

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